1. Field of Invention
This invention relates to radio communication apparatus and methods and more particularly to apparatus and methods facilitating the use and monitoring of multiple radio frequency channels.
2. Description of Related Art
Communication between wearers of self-contained breathing apparatus, such as face masks, for example, is extremely difficult even under the best conditions. Users must yell through their masks or use hand signals, or in some cases, even remove their masks, just to be able to communicate with each other. Communication among fire fighters, for example, can become almost impossible in a smoke-filled or fire engulfed area. Fire fighting often requires split-second decision making, often with serious consequences at stake, and thus communication between fire fighters is important.
Existing communication mechanisms typically employ a very high frequency (VHF) or ultra high frequency (UHF) radio connected to a microphone which is “push-to-talk” activated and coupled by a corded link to a speaker placed in proximity to a user's ear. This may provide a walkie-talkie type arrangement for single-channel communications. When using this type of system, a wearer of a self-contained breathing apparatus must push a button while speaking into the microphone, which requires the use of one hand, leaving only one hand free. Moreover, audio signals picked up by the microphone are usually amplified before transmission and often the microphone picks up interference in the form of ambient noise, such as the noise encountered in most fire situations for example. In addition, the geometry of a cavity inside the self-contained breathing apparatus can enhance low frequencies, making the wearer's voice virtually unintelligible when transmitted to a remote user. The cord connecting the microphone and speaker to the VHF or UHF radio can often frustrate a user as it can become entangled in the user's clothes or other equipment in use, or it may loosen and become detached. In short, the cord can be a safety hazard, which is of particular concern in the case of fire fighters.
Some existing mechanisms employ voice detection circuitry as an alternative to or in addition to the “push-to-talk” function. However, ambient noise interference can cause false triggering of the voice detection circuitry.
Existing mechanisms that permit a user to choose between “push-to-talk” operation and hands-free operation require that the user unplug a cable from one receptacle and plug the cable into another. There is not a seamless transition between “push-to-talk” operation and hands-free operation, which can be a problem as fire fighters suit up to attend a fire.